1. Field of the Invention
The present invention generally relates to ribbon cables and more particularly to a ribbon cable which includes vent tubes that allow for pressure equalization while simultaneously minimizing the risk of unwanted intrusion.
2. Description of the Related Art
Flat ribbon cables are useful in many environments and are especially useful for encapsulated enclosures. For example, a cryptographic processor card (crypto-card) which complies with FIPS (Federal Information Processing Standard) Level 4 (highest possible security) must be capable of detecting any intrusion into the encapsulated enclosure containing protected data, uses ribbon cables.
Such a crypto-card and its enclosure are completely surrounded by a xe2x80x9ctamper detection meshxe2x80x9d from which one or more flat ribbon cables protrude through folds in the mesh. The assembly is fully encapsulated, with the exception of protruding cables, in a resin system tailored to the mesh materials. Any attempt subsequent loss (erasure) of vital security data resident on the crypto-card in order to prevent unauthorized access to critical data being stored on or transmitted by the crypto-card.
The encapsulation of the crypto-card enclosure assembly, the tamper detection mesh, and the pressure differentials which can form between the inside of the enclosure and the outside atmosphere result in stresses on the assembly, particularly the tamper detection mesh. The pressure differentials arise from thermal conditions, changes in barometric pressure and altitude changes. Therefore, there is a need for ventilation of the crypto-card enclosure assembly which does not compromise the integrity of the enclosure.
It is, therefore, an object of the present invention to provide an encapsulated enclosure having a ribbon cable that includes electrical conductors surrounded by an insulator and vent tubes positioned adjacent and parallel to the conductors and insulator. The vent tubes allow airflow between an internal area of the enclosure and an external atmosphere and prevent access to the internal area of the enclosure.
The vent tubes can be connected externally to the ribbon cable or positioned internally within the ribbon cable. There can also be a mesh within the vent tubes which can include fused contacts at the ends of the vent tubes to allow an electrical connection to be made. The ribbon cable can include a card connector for being inserted into a connector housing and the ends of the vent tubes are positioned approximately 5-20 mils from the connector housing. The vent tubes have a diameter of approximately 5-10 mils.